A wind turbine known in the art comprises a wind turbine tower and a wind turbine nacelle positioned on top of the tower. A wind turbine rotor with three wind turbine blades is connected to the nacelle through a low speed shaft, which extends out of the nacelle front as illustrated on FIG. 1.
Thermal stress to components containing or comprising materials of different temperature expand coefficients is a well know problem, and within the art of making wind turbines this problem is particularly pronounced.
Thermal stress basically originates from two factors—High temperature and more importantly varying temperatures.
Arrhenius' exponential “law”, which is a well proven theory, suggest that the higher the temperature, the faster a given chemical reaction will proceed and e.g. regarding electrical components, a rule of thumb says that for every 10° C. the temperature is raised, the risk of failures doubles. So to ensure long life of the wind turbines heat generating and/or passive components such as power converters, generators, control systems, gears and hydraulic systems it is known to provide these components with some sort of temperature control, often in form of cooling systems keeping the components operating temperature below a certain level.
The problem with this solution is, that the ambient temperature varies a lot from site to site, from day to night and from season to season. This combined with the variation in internal heat production, due to varying wind conditions and thereby varying power production, makes the components temperature vary a lot both during the day and night and during the year. Furthermore it is very difficult to estimate the life of the components if there is no or very little control with the size and number of temperature fluctuations.
Varying temperatures in heat generating and/or passive components is a big problem, mainly because of the fact that different materials have different coefficients of thermal expansion, but also because e.g. lubricants and interacting mechanical components are made to work optimally at a specific temperature.
The solution to this problem would be to maintain the components temperature fixed at all times. But this would demand a cooling and heating system with a very high capacity, which would be expensive in both manufacturing, operating and maintenance costs. Furthermore such a system or systems would be both big and heavy which is particularly disadvantageous in the art of making wind turbines.
An object of the invention is therefore to provide a temperature control system for heat generating and/or passive components in or at a wind turbine without the mentioned disadvantages.
Furthermore it is an object of the invention to provide for a cost efficient temperature control system that reduces the thermal stress in the heat generating and/or passive components of a wind turbine.
Especially it is an object of the invention to provide for a cost efficient temperature control system that controls the thermal stress in the heat generating and/or passive components of a wind turbine.